Senior Frontend Engineer, AI Observability & Evals Platform

About Us

At Lang Chain, our mission is to make intelligent agents ubiquitous. We build the foundation for agent engineering in the real world, helping developers move from prototypes to production-ready AI agents that teams can rely on. We began as widely adopted open-source tools and have grown to also offer a platform for building, evaluating, deploying, and operating agents ay, Lang Chain, Lang Graph, Lang Smith, and Agent Builder are used by teams shipping real AI products across startups and large enterprises.

Millions of developers trust Lang Chain to power AI teams at companies like Replit, Clay, Coinbase, Workday, Lyft, Cloudflare, Harvey, Rippling, Vanta, and 35% of the Fortune 500. With $125M raised at Series B from IVP, Sequoia, Benchmark, Capital

G, and Sapphire Ventures, we’re continuing to develop new products and expand.

In person 5 days/week in San Francisco, CA, New York, Boston. We’re looking to add a frontend engineer to develop and enhance new features on Lang Smith, our enterprise platform product for LLM application observability, testing, and debugging. You will:

• Develop new user-facing features using React & Typescript
• Build reusable components and front-end libraries for future use
• Translate designs and wireframes into high-quality code
• Optimize components for maximum performance across a vast array of web-capable devices and browsers
• Collaborate with fullstack and backend developers and UX/UI designers to enhance usability

• Front-end engineering experience with strong proficiency in React, JavaScript and Type Script
• Hands-on experience with front-end development tools like Babel, Vite, Webpack, NPM, and Yarn
• Familiarity with REST APIs and experience working closely with fullstack and backend engineers
• Knowledge of modern authorization mechanisms, such as JWTs
• A passion for user experience, design and building clean, engaging, and intuitive interfaces
• Strong written and oral communication skills, with the ability to explain technical concepts clearly and concisely to both technical and non-technical stakeholders
• The DNA to thrive in a start-up, fast-paced environment
• An ownership mind-set and self-driven attitude
• Strong computer science fundamentals, ideally with a degree in computer science or related field

• Competitive compensation that includes base salary, meaningful equity, and benefits such as health and dental coverage, flexible vacation, a 401(k) plan, and life insurance. Actual compensation will vary based on role, level, and location. For team members in the EU and UK, we provide locally competitive benefits aligned with regional norms and regulations.
• Annual salary range: $175,000-$225,000 USD